Hybrid vehicle and control method thereof

ABSTRACT

A hybrid vehicle includes a multi-cylinder engine, an exhaust gas control apparatus, an electric motor, an electricity storage device, and a controller. The controller is configured to control the electric motor so as to cover a driving power shortage resulting from execution of catalyst temperature raising control. The catalyst temperature raising control is control that involves stopping fuel supply to at least one of cylinders of the multi-cylinder engine and enriching air-fuel ratios for the other cylinders than the at least one cylinder.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2019-186129 filed onOct. 9, 2019 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

This disclosure relates to a hybrid vehicle and a control methodthereof.

2. Description of Related Art

There is a known controller that, when an SOx-poisoning amount of acatalytic device disposed in an exhaust passage of an internalcombustion engine exceeds a predetermined value, executes catalysttemperature raising control (dither control) involving setting air-fuelratios for some of the cylinders (rich cylinders) to rich ratios whilesetting air-fuel ratios for other cylinders (lean cylinders) to leanratios (see, e.g., Japanese Unexamined Patent Application PublicationNo. 2004-218541). This controller sets each of the degree of richnessfor the rich cylinders and the degree of leanness for the lean cylindersto a different degree at an initiation stage of the temperature raisingcontrol and at a later stage. Further, this controller changes thedegree of richness and the degree of leanness as time passes from thestart of the temperature raising control such that the degree ofrichness and the degree of leanness become lower at the initiation stageof the temperature raising control. This makes it possible to raise thetemperature of the catalytic device while reducing the likelihood ofmisfiring in the lean cylinders.

There is another known controller that sequentially executes ignitiontiming retarding control, fuel-cutoff-and-rich-burn control, andlean-burn-and-rich-burn control (dither control) as catalyst temperatureraising control for warming up a catalytic device that removes harmfulcomponents of exhaust gas from an internal combustion engine (see, e.g.,Japanese Unexamined Patent Application Publication No. 2011-069281). Theignition timing retarding control involves retarding the ignition timingto warm up the catalytic device with high-temperature exhaust gas. Thefuel-cutoff-and-rich-burn control involves making a cylinder to whichfuel injection is stopped with an intake valve and an exhaust valve keptoperating and a cylinder into which fuel is injected so as to enrich theair-fuel ratio alternate with each other. The fuel-cutoff-and-rich-burncontrol is executed for about three seconds when the temperature at acatalyst inlet reaches a first temperature as a result of the ignitiontiming retarding control. Thus, oxygen and uncombusted gas are sent tothe catalytic device, and the catalytic device is warmed up with theheat of an oxidation reaction. When the temperature at the catalystinlet reaches a second temperature higher than the first temperature,the lean-burn-and-rich-burn control is executed until the temperature ata catalyst outlet reaches the second temperature.

Among known controllers of a hybrid vehicle including an internalcombustion engine and an electric motor, there is one that stops fuelsupply to each cylinder of the internal combustion engine when powerrequired of the internal combustion engine becomes smaller than athreshold value, and controls the electric motor so as to output atorque based on a required torque and a correction torque at a timingwhen a correction start time has elapsed from the start of fuel cutoff.This controller estimates, based on the speed and the number of thecylinders of the internal combustion engine, a shortest time and alongest time from the start of fuel cutoff until a torque shock due tothe fuel cutoff starts to occur, and sets a time between the shortesttime and the longest time as the correction start time. The correctiontorque is determined so as to offset the torque shock acting on a driveshaft.

SUMMARY

Executing these methods of catalyst temperature raising control cannotalways send sufficient air, i.e., oxygen to a catalytic device andsufficiently raise the temperature of the catalytic device, if theenvironmental temperature is low or the temperature required to beachieved by catalyst temperature raising control is high. Moreover, itis not easy to introduce the amount of oxygen required to regenerate acatalyst or a particulate filter of an exhaust gas control apparatusinto the exhaust gas control apparatus by these methods of catalysttemperature raising control. When executing catalyst temperature raisingcontrol during load operation of an internal combustion engine, it isnecessary to avoid deteriorating the drivability of the vehicle equippedwith the internal combustion engine.

Therefore, this disclosure provides a hybrid vehicle and a controlmethod thereof that are configured to, during load operation of amulti-cylinder engine, sufficiently and quickly raise the temperature ofa catalyst of an exhaust gas control apparatus and supply a sufficientamount of oxygen to the exhaust gas control apparatus while avoidingdeteriorating the drivability of the vehicle.

A hybrid vehicle according to a first aspect of this disclosure includesa multi-cylinder engine, an exhaust gas control apparatus, an electricmotor, an electricity storage device, and a controller. The exhaust gascontrol apparatus is configured to remove harmful components of exhaustgas from the multi-cylinder engine. The electricity storage device isconfigured to exchange electricity with the electric motor. In thehybrid vehicle in which at least one of the multi-cylinder engine andthe electric motor is configured to output driving power to a wheel, thecontroller is configured to execute catalyst temperature raising controlupon request for raising the temperature of the catalyst during loadoperation of the multi-cylinder engine. The controller is configured tocontrol the electric motor so as to cover a driving power shortageresulting from execution of the catalyst temperature raising control.The catalyst temperature raising control is control that involvesstopping fuel supply to at least one of cylinders of the multi-cylinderengine and enriching air-fuel ratios for the other cylinders than the atleast one cylinder.

In the hybrid vehicle according to the first aspect of this disclosure,the controller may be configured to control the electric motor so as tocover the driving power shortage while fuel supply to the at least onecylinder of the multi-cylinder engine is stopped. In the hybrid vehicleaccording to the first aspect of this disclosure, the controller may beconfigured to retard an ignition timing for the other cylinders so as toavoid an increase in an output of the multi-cylinder engine resultingfrom enrichment of the air-fuel ratios for the other cylinders.

The hybrid vehicle according to the first aspect of this disclosure mayfurther include a second electric motor configured to convert at leastpart of power from the multi-cylinder engine into electricity and toexchange electricity with the electricity storage device. The controllermay be configured to control the second electric motor so as to convertexcess power of the multi-cylinder engine resulting from enrichment ofthe air-fuel ratios for the other cylinders into electricity. In thehybrid vehicle according to the first aspect of this disclosure, thecontroller may be configured to retard an ignition timing for the othercylinders when the second electric motor is unable to convert the excesspower of the multi-cylinder engine into electricity.

The hybrid vehicle according to the first aspect of this disclosure mayfurther include a transaxle that is coupled to an output shaft of themulti-cylinder engine, the second electric motor, and the wheel. Theelectric motor may be configured to output the driving power to thewheel or another wheel different from the wheel. In the hybrid vehicleaccording to the first aspect of this disclosure, the exhaust gascontrol apparatus may include a particulate filter.

In a control method of a hybrid vehicle according to a second aspect ofthis disclosure, the hybrid vehicle includes a multi-cylinder engine, anexhaust gas control apparatus including a catalyst configured to removeharmful components of exhaust gas from the multi-cylinder engine, anelectric motor, and an electricity storage device configured to exchangeelectricity with the electric motor. In the hybrid vehicle, at least oneof the multi-cylinder engine and the electric motor is configured tooutput driving power to a wheel. The control method of the hybridvehicle includes: upon request for raising the temperature of thecatalyst during load operation of the multi-cylinder engine, executingcatalyst temperature raising control that involves stopping fuel supplyto at least one of cylinders and enriching air-fuel ratios for the othercylinders than the at least one cylinder; and controlling the electricmotor so as to cover a driving power shortage resulting from executionof the catalyst temperature raising control.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a schematic configuration diagram showing a hybrid vehicle ofthis disclosure;

FIG. 2 is a schematic configuration diagram showing a multi-cylinderengine included in the hybrid vehicle of FIG. 1 ;

FIG. 3 is a flowchart illustrating a routine of determining whether ornot a particulate filter needs to be regenerated that is executed in thehybrid vehicle of FIG. 1 ;

FIG. 4 is a flowchart illustrating a catalyst temperature raisingcontrol routine that is executed in the hybrid vehicle of FIG. 1 ;

FIG. 5 is a flowchart illustrating the catalyst temperature raisingcontrol routine that is executed in the hybrid vehicle of FIG. 1 ;

FIG. 6 is a flowchart illustrating a driving control routine that isexecuted in the hybrid vehicle of FIG. 1 ;

FIG. 7 is a graph showing a relationship between a torque output fromthe multi-cylinder engine and ignition timing;

FIG. 8 is a time chart showing the operating state of the multi-cylinderengine and changes in the temperature of the particulate filter duringexecution of the routines shown in FIG. 4 to FIG. 6 ;

FIG. 9 is a schematic configuration diagram showing another hybridvehicle of this disclosure;

FIG. 10 is a schematic configuration diagram showing yet another hybridvehicle of this disclosure;

FIG. 11 is a schematic configuration diagram showing another hybridvehicle of this disclosure; and

FIG. 12 is a schematic configuration diagram showing still anotherhybrid vehicle of this disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Next, a mode for carrying out the applicable embodiment of thisdisclosure will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing a hybrid vehicle 1of this disclosure. The hybrid vehicle 1 shown in FIG. 1 includes: amulti-cylinder engine (hereinafter referred to simply as an “engine”) 10having a plurality of (in this embodiment, e.g., four) cylinders(combustion chambers) 11; a single-pinion planetary gear 30; motorgenerators MG1, MG2 that are both synchronous generator-motors(three-phase alternating-current electric motors); an electricitystorage device (battery) 40; a power control unit (hereinafter referredto as a “PCU”) 50 that is connected to the electricity storage device 40and drives the motor generators MG1, MG2; an electronically controlledhydraulic braking device 60 that can apply a frictional braking force toa wheel W; and a hybrid electronic control unit (hereinafter referred toas an “HVECU”) 70 that controls the entire vehicle.

The engine 10 is an in-line gasoline engine (internal combustion engine)that converts reciprocating motion of pistons (not shown) accompanyingcombustion of a mixture of hydrocarbon fuel and air in the cylinders 11into rotating motion of a crankshaft (output shaft) 12. As shown in FIG.2 , the engine 10 includes an intake pipe 13, an intake manifold 13 m, athrottle valve 14, a plurality of intake valves and a plurality ofexhaust valves (neither is shown), a plurality of port injection valves15 p, a plurality of cylinder injection valves 15 d, a plurality ofspark plugs 16, an exhaust manifold 17 m, and an exhaust pipe 17. Thethrottle valve 14 is an electronically controlled throttle valve thatcan change the area of passage inside the intake pipe 13. The intakemanifold 13 m is connected to the intake pipe 13 and an intake port ofeach cylinder 11. Each port injection valve 15 p injects fuel into thecorresponding intake port, and each cylinder injection valve 15 dinjects fuel directly into the corresponding cylinder 11. The exhaustmanifold 17 m is connected to an exhaust port of each cylinder 11 andthe exhaust pipe 17.

The engine 10 includes a low-pressure delivery pipe DL that is connectedto a feed pump (low-pressure pump) Pf through a low-pressure fuel supplypipe LL, and a high-pressure delivery pipe DH that is connected to asupply pump (high-pressure pump) Ps through a high-pressure fuel supplypipe LH. The low-pressure delivery pipe DL is connected to a fuel inletof each port injection valve 15 p, and the high-pressure delivery pipeDH is connected to a fuel inlet of each cylinder injection valve 15 d.The feed pump Pf is an electrically powered pump including a motor thatis driven with electricity from an auxiliary battery (not shown). Fuelfrom the feed pump Pf is stored in the low-pressure delivery pipe DL andsupplied from the low-pressure delivery pipe DL to each port injectionvalve 15 p. The supply pump Ps is, for example, a piston pump(mechanical pump) driven by the engine 10. High-pressure fuel from thesupply pump Ps is stored inside the high-pressure delivery pipe DH andsupplied from the high-pressure delivery pipe DH to each cylinderinjection valve 15 d.

As shown in FIG. 2 , the engine 10 further includes an evaporated fuelprocessing device 110 that introduces, into the intake manifold 13 m,evaporated fuel that is generated inside a fuel tank Tk holding fuel.The evaporated fuel processing device 110 includes a canister 111containing an adsorbent (active carbon) that adsorbs evaporated fuelinside the fuel tank Tk, a vapor passage Lv connecting the fuel tank Tkand the canister 111 to each other, a purge passage Lp connecting thecanister 111 and the intake manifold 13 m to each other, and a purgevalve (vacuum switching valve) Vsv installed in the purge passage Lp. Inthis embodiment, the purge valve Vsv is a control valve of which theopening degree is adjustable.

The engine 10 further includes, as exhaust gas control apparatuses, anupstream control apparatus 18 and a downstream control apparatus 19 thatare both incorporated in the exhaust pipe 17. The upstream controlapparatus 18 includes an NOx-storing exhaust gas control catalyst(three-way catalyst) 180 that removes harmful components, such as CO(carbon monoxide), HC, and NOx, of exhaust gas from each cylinder 11 ofthe engine 10. The downstream control apparatus 19 includes aparticulate filter (GPF) 190 that is disposed downstream of the upstreamcontrol apparatus 18 and collects particulate matter (fine particles) inthe exhaust gas. In this embodiment, the particulate filter 190 is afilter that supports an NOx-storing exhaust gas control catalyst(three-way catalyst).

The engine 10 is controlled by an engine electronic control unit(hereinafter referred to as an “engine ECU”) 100. The engine ECU 100includes a microcomputer having a CPU, ROM, RAM, input-output interface,etc., various driving circuits, and various logic ICs (none is shown),and executes intake air amount control, fuel injection control, andignition timing control over the engine 10, purge control forcontrolling the amount of evaporated fuel purged by the evaporated fuelprocessing device 110 (purge valve Vsv), etc. The engine ECU 100acquires, through an input port (not shown), detection values of a crankangle sensor 90, a coolant temperature sensor 91, an air flowmeter 92,an intake air pressure sensor (not shown), a throttle valve positionsensor (not shown), an upstream air-fuel ratio sensor 95, a downstreamair-fuel ratio sensor 96, a differential pressure sensor 97, an upstreamcatalyst temperature sensor 98, a downstream catalyst temperature sensor99, etc.

The crank angle sensor 90 detects a rotation position of the crankshaft12 (crank position). The coolant temperature sensor 91 detects a coolanttemperature Tw of the engine 10. The air flowmeter 92 detects an intakeair amount GA of the engine 10. The intake air pressure sensor detects apressure inside the intake pipe 13, i.e., an intake air pressure. Thethrottle valve position sensor detects the position of a valve disc ofthe throttle valve 14 (throttle position). The upstream air-fuel ratiosensor 95 detects an upstream air-fuel ratio AFf that is an air-fuelratio of exhaust gas flowing into the upstream control apparatus 18. Thedownstream air-fuel ratio sensor 96 detects a downstream air-fuel ratioAFr that is an air-fuel ratio of exhaust gas flowing into the downstreamcontrol apparatus 19. The differential pressure sensor 97 detects adifferential pressure ΔP between an upstream side and a downstream sideof the downstream control apparatus 19, i.e., the particulate filter190. The upstream catalyst temperature sensor 98 detects a temperature(catalyst temperature) Tct of the upstream control apparatus 18, i.e.,the exhaust gas control catalyst 180. The downstream catalysttemperature sensor 99 detects a temperature (catalyst temperature) Tpfof the downstream control apparatus 19, i.e., the particulate filter190.

The engine ECU 100 calculates a speed Ne of the engine 10 (crankshaft12) based on the crank position from the crank angle sensor 90. Further,the engine ECU 100 calculates (estimates) a build-up amount Dpm ofparticulate matter on the particulate filter 190 of the downstreamcontrol apparatus 19 at predetermined time intervals by either a drivinghistory method or a differential pressure method according to a drivingstate of the engine 10 etc. When using the differential pressure method,the engine ECU 100 calculates the build-up amount Dpm based on thedifferential pressure ΔP detected by the differential pressure sensor97, i.e., a pressure loss at the particulate filter 190 due to buildingup of particulate matter. When using the driving history method, theengine ECU 100 calculates the build-up amount Dpm (current value) byadding an estimated increase amount (positive value) or an estimateddecrease amount (negative value) of particulate matter to the last valueof the build-up amount Dpm according to the driving state of the engine10. The estimated increase amount of particulate matter is calculated,for example, as the product of an estimated amount of particulate matteremitted that is calculated from the speed Ne, a load factor, and thecoolant temperature Tw of the engine 10; an emission factor; and thecollection efficiency of the particulate filter 190. The estimateddecrease amount of particulate matter is calculated, for example, as theproduct of an amount of particulate matter combusted that is calculatedfrom the last value of the build-up amount Dpm, a flow rate of inflowair, and the temperature Tpf of the particulate filter 190; and acorrection factor.

The engine 10 may be a diesel engine having a diesel particulate filter(DPF) or an LPG engine. The temperatures Tct, Tpf of the exhaust gascontrol catalyst 180 and the particulate filter 190 may be estimatedbased on the intake air amount GA, the speed Ne, the temperature ofexhaust gas, the upstream air-fuel ratio AFf, the downstream air-fuelratio AFr, etc.

The planetary gear 30 is a differential rotating mechanism including asun gear (first element) 31, a ring gear (second element) 32, and aplanetary carrier (third element) 34 that rotatably supports a pluralityof pinion gears 33. As shown in FIG. 1 , the sun gear 31 is coupled to arotor of the motor generator MG1, and the planetary carrier 34 iscoupled to the crankshaft 12 of the engine 10 through a damper mechanism24. The ring gear 32 is integrated with a counter drive gear 35 actingas an output member, and these gears rotate coaxially and integrally.

The counter drive gear 35 is coupled to left and right wheels (drivingwheels) W through a counter driven gear 36 meshing with the counterdrive gear 35, a final drive gear (drive pinion gear) 37 rotatingintegrally with the counter driven gear 36, a final driven gear(differential ring gear) 39 r meshing with the final drive gear 37, adifferential gear 39, and a drive shaft DS. Thus, the planetary gear 30,the gear train from the counter drive gear 35 to the final driven gear39 r, and the differential gear 39 constitute a transaxle 20 thattransmits part of an output torque of the engine 10 acting as a motivepower generation source to the wheels W and couples together the engine10 and the motor generator MG1.

The drive gear 38 is fixed to a rotor of the motor generator MG2. Thedrive gear 38 has fewer teeth than the counter driven gear 36 and mesheswith the counter driven gear 36. Thus, the motor generator MG2 iscoupled to the left and right wheels W through the drive gear 38, thecounter driven gear 36, the final drive gear 37, the final driven gear39 r, the differential gear 39, and the drive shaft DS.

The motor generator MG1 (second electric motor) operates mainly as apower generator that converts at least part of power from the engine 10in load operation into electricity. The motor generator MG2 operatesmainly as an electric motor that is driven with at least one ofelectricity from the electricity storage device 40 and electricity fromthe motor generator MG1 and generates a driving torque to the driveshaft DS. Thus, in the hybrid vehicle 1, the motor generator MG2 as amotive power generation source functions as a motive power generatingdevice that, together with the engine 10, outputs a driving torque(driving power) to the wheels W mounted on the drive shaft DS. Further,the motor generator MG2 outputs a regenerative braking torque to brakethe hybrid vehicle 1. The motor generators MG1, MG2 can exchangeelectricity with the electricity storage device 40 through the PCU 50and also exchange electricity with each other through the PCU 50.

The electricity storage device 40 is, for example, a lithium-ionsecondary battery or a nickel-metal hydride secondary battery. Theelectricity storage device 40 is managed by a power source managingelectronic control unit (hereinafter referred to as a “power sourcemanaging ECU”) 45 including a microcomputer having a CPU, ROM, RAM,input-output interface, etc. (none is shown). The power source managingECU 45 derives a state-of-charge (SOC), allowable charge electricityWin, allowable discharge electricity Wout, etc. of the electricitystorage device 40 based on a voltage VB between terminals from a voltagesensor of the electricity storage device 40, a charge-discharge currentIB from a current sensor thereof, a battery temperature Tb from atemperature sensor 47 thereof (see FIG. 1 ), etc.

The PCU 50 includes a first inverter 51 that drives the motor generatorMG1, a second inverter 52 that drives the motor generator MG2, and aboost converter (voltage conversion module) 53 that can step up thevoltage of electricity from the electricity storage device 40 and stepdown the voltage of electricity from the motor generators MG1, MG2. ThePCU 50 is controlled by a motor electronic control unit (hereinafterreferred to as an “MGECU”) 55 including a microcomputer having a CPU,ROM, RAM, input-output interface, etc., various driving circuits, andvarious logic ICs (none is shown). The MGECU 55 acquires a commandsignal from the HVECU 70, voltages before and after being stepped up bythe boost converter 53, detection values of resolvers (none is shown)that detect the rotation positions of the rotors of the motor generatorsMG1, MG2, phase currents applied to the motor generators MG1, MG2, etc.Based on these signals etc., the MGECU 55 controls switching of thefirst and second inverters 51, 52 and the boost converter 53. Based onthe detection values of the resolvers, the MGECU 55 calculates rotationspeeds Nm1, Nm2 of the rotors of the motor generators MG1, MG2.

The hydraulic braking device 60 includes: a master cylinder; a pluralityof brake pads (not shown) that holds therebetween a brake disc mountedon each wheel W and applies a braking torque (frictional braking torque)to the corresponding wheel; a plurality of wheel cylinders (not shown)that drives the corresponding brake pad; a hydraulic brake actuator 61that supplies hydraulic pressure to each wheel cylinder; and a brakeelectronic control unit (hereinafter referred to as a “brake ECU”) 65that controls the brake actuator 61. The brake ECU 65 includes amicrocomputer having a CPU, ROM, RAM, input-output interface, etc. (noneis shown). The brake ECU 65 acquires a command signal from the HVECU 70,a brake pedal stroke BS (an amount of pressing on a brake pedal 64)detected by the brake pedal stroke sensor 63, a vehicle speed V detectedby a vehicle speed sensor (not shown), etc. The brake ECU 65 controlsthe brake actuator 61 based on these signals etc.

The HVECU 70 includes a microcomputer having a CPU, ROM, RAM,input-output interface, etc., various driving circuits, and variouslogic ICs (none is shown). The HVECU 70 exchanges information(communication frames) with the ECUs 100, 45, 55, 65, etc. through acommon communication line (multiplex communication bus; not shown) thatis a CAN bus including two Lo and Hi communication lines (wireharnesses). The HVECU 70 is separately connected to each of the ECUs100, 45, 55, 65 through a dedicated communication line (localcommunication bus) that is a CAN bus including Lo and Hi twocommunication lines (wire harnesses). The HVECU 70 exchanges information(communication frames) separately with each of the ECUs 100, 45, 55, 65through the corresponding dedicated communication line. Further, theHVECU 70 acquires signals from a start switch (not shown) that orderssystem start of the hybrid vehicle 1, a shift position SP of a shiftlever 82 detected by a shift position sensor 81, an acceleratoroperation amount Acc (an amount of pressing on an accelerator pedal 84)detected by an accelerator pedal position sensor 83, the vehicle speed Vdetected by the vehicle speed sensor (not shown), the crank positiondetected by the crank angle sensor 90 of the engine 10, etc. Further,the HVECU 70 acquires the state-of-charge (SOC), the allowable chargeelectricity Win, and the allowable discharge electricity Wout of theelectricity storage device 40 from the power source managing ECU 45, therotation speeds Nm1, Nm2 of the motor generators MG1, MG2 from the MGECU55, etc.

When the hybrid vehicle 1 travels, the HVECU 70 derives, from a requiredtorque setting map (not shown), a required torque Tr* (including arequired braking torque) to be output to the drive shaft DScorresponding to the accelerator operation amount Acc and the vehiclespeed V. Based on the required torque Tr* and a rotating speed Nds ofthe drive shaft DS, the HVECU 70 sets required travel power Pd*(=Tr*×Nds) required for the hybrid vehicle 1 to travel. Based on therequired torque Tr*, the required travel power Pd*, separately settarget charge-discharge electricity Pb* and the allowable dischargeelectricity Wout of the electricity storage device 40, etc., the HVECU70 determines whether or not to perform load operation of the engine 10.

When performing load operation of the engine 10, the HVECU 70 setsrequired power Pe* (=Pd*−Pb*+Loss) of the engine 10 based on therequired travel power Pd*, the target charge-discharge electricity Pb*,etc. Further, the HVECU 70 sets a target speed Ne* of the engine 10according to the required power Pe* such that the engine 10 isefficiently operated and does not fall below a lower limit speed Nelimaccording to the driving state of the hybrid vehicle 1 etc. Then, theHVECU 70 sets, within the ranges of the allowable charge electricity Winand the allowable discharge electricity Wout of the electricity storagedevice 40, torque commands Tm1*, Tm2* for the motor generators MG1, MG2according to the required torque Tr*, the target speed Ne*, etc. On theother hand, when stopping the operation of the engine 10, the HVECU 70sets the required power Pe*, the target speed Ne*, and the torquecommand Tm1* to zero. Further, the HVECU 70 sets the torque command Tm2*within the ranges of the allowable charge electricity Win and theallowable discharge electricity Wout of the electricity storage device40 such that a torque according to the required torque Tr* is outputfrom the motor generator MG2 to the drive shaft DS.

Then, the HVECU 70 sends the required power Pe* and the target speed Ne*to the engine ECU 100 and sends the torque commands Tm1*, Tm2* to theMGECU 55. Based on the required power Pe* and the target speed Ne*, theengine ECU 100 executes intake air amount control, fuel injectioncontrol, ignition timing control, etc. In this embodiment, the engineECU 100 basically executes the fuel injection control such that theair-fuel ratio for each cylinder 11 of the engine 10 becomes thestoichiometric air-fuel ratio (=14.6 to 14.7). When the load on (therequired power Pe* of) the engine 10 is equal to or smaller than apredetermined value, fuel is injected from each port injection valve 15p, and fuel injection from each cylinder injection valve 15 d isstopped. While the load on the engine 10 exceeds the predeterminedvalue, fuel injection from each port injection valve 15 p is stopped andfuel is injected from each cylinder injection valve 15 d. In thisembodiment, fuel injection and ignition of the cylinders 11 are executedin the (ignition) order of a first cylinder #1, a third cylinder #3, afourth cylinder #4, and a second cylinder #2.

The MGECU 55 controls switching of the first and second inverters 51, 52and the boost converter 53 based on the torque commands Tm1*, Tm2*. Whenthe engine 10 performs load operation, the motor generators MG1, MG2 arecontrolled so as to convert, together with the planetary gear 30, partof power output from the engine 10 (when the electricity storage device40 is being charged) or the whole of the power (when the electricitystorage device 40 is being discharged) into a torque and output thistorque to the drive shaft DS. Thus, the hybrid vehicle 1 travels onpower from the engine 10 (a directly transmitted torque) and power fromthe motor generator MG2 (HV travel). On the other hand, when the engine10 stops operating, the hybrid vehicle 1 travels only on power (adriving torque) from the motor generator MG2 (EV travel).

Here, as described above, the hybrid vehicle 1 of this embodimentincludes the downstream control apparatus 19 having the particulatefilter 190 as the exhaust gas control apparatus. The build-up amount Dpmof particulate matter (“PM”) on the particulate filter 190 increases asthe distance traveled by the hybrid vehicle 1 increases and as theenvironmental temperature becomes lower. Therefore, at a stage where thebuild-up amount Dpm of particulate matter on the particulate filter 190has increased, the hybrid vehicle 1 needs to combust the particulatematter and regenerate the particulate filter 190 by sending a largeamount of air, i.e., oxygen to the particulate filter 190 of which thetemperature has been sufficiently raised. To do so, the engine ECU 100of the hybrid vehicle 1 executes a routine of determining whether or notthe particulate filter needs to be regenerated, illustrated in FIG. 3 ,at predetermined time intervals when load operation of the engine 10 isperformed according to a driver of the hybrid vehicle 1 pressing on theaccelerator pedal 84.

At the start of the routine of FIG. 3 , the engine ECU 100 acquiresinformation required for the determination, such as the intake airamount GA, the speed Ne, and the coolant temperature Tw of the engine10, and the temperature Tpf of the particulate filter 190 (step S100).Based on the physical quantities etc. acquired in step S100, the engineECU 100 calculates the build-up amount Dpm of particulate matter on theparticulate filter 190 by either the driving history method or thedifferential pressure method according to the operating state of theengine 10 etc. (step S110). Then, the engine ECU 100 determines whetheror not a catalyst temperature raising control routine for raising thetemperatures of the exhaust gas control catalyst 180 of the upstreamcontrol apparatus 18 and the particulate filter 190 of the downstreamcontrol apparatus 19 is yet to be executed (step S120).

When it is determined in step S120 that the catalyst temperature raisingcontrol routine is yet to be executed (step S120: YES), the engine ECU100 determines whether or not the build-up amount Dpm calculated in stepS110 is equal to or larger than a predetermined threshold value D1(e.g., a value of about 5000 mg) (step S130). When it is determined instep S130 that the build-up amount Dpm is smaller than the thresholdvalue D1 (step S130: NO), the engine ECU 100 ends the routine of FIG. 3at that point for now. When it is determined in step S130 that thebuild-up amount Dpm is equal to or larger than the threshold value D1(step S130: YES), the engine ECU 100 determines whether or not thetemperature Tpf of the particulate filter 190 acquired in step S100 islower than a predetermined temperature raising control start temperature(predetermined temperature) Tx (step S140). The temperature raisingcontrol start temperature Tx is determined in advance according to theservice environment of the hybrid vehicle 1, and is, for example, atemperature of around 600° C. in this embodiment.

When it is determined in step S140 that the temperature Tpf of theparticulate filter 190 is equal to or higher than the temperatureraising control start temperature Tx (step S140: NO), the engine ECU 100ends the routine of FIG. 3 at that point for now. When it is determinedin step S140 that the temperature Tpf of the particulate filter 190 islower than the temperature raising control start temperature Tx (stepS140: YES), the engine ECU 100 sends a catalyst temperature rise requestsignal for requesting execution of the catalyst temperature raisingcontrol routine to the HVECU 70 (step S150), and ends the routine ofFIG. 3 for now. When execution of the catalyst temperature raisingcontrol routine is permitted by the HVECU 70 after the catalysttemperature rise request signal is sent, the engine ECU 100 turns acatalyst temperature rise flag on and starts the catalyst temperatureraising control routine.

On the other hand, when it is determined in step S120 that the catalysttemperature raising control routine is already executed (step S120: NO),the engine ECU 100 determines whether or not the build-up amount Dpmcalculated in step S110 is equal to or smaller than a predeterminedthreshold value D0 (e.g., a value of about 3000 mg) that is smaller thanthe threshold value D1 (step S160). When it is determined in step S160that the build-up amount Dpm exceeds the threshold value D0 (step S160:NO), the engine ECU 100 ends the routine of FIG. 3 at that point fornow. When it is determined in step S160 that the build-up amount Dpm isequal to or smaller than the threshold value D0 (step S160: YES), theengine ECU 100 turns the catalyst temperature rise flag off, ends thecatalyst temperature raising control routine (step S170), and ends theroutine of FIG. 3 .

Next, the catalyst temperature raising control routine for raising thetemperatures of the exhaust gas control catalyst 180 and the particulatefilter 190 will be described. FIG. 4 is a flowchart illustrating thecatalyst temperature raising control routine that is executed by theengine ECU 100 at predetermined time intervals. The routine of FIG. 4 isexecuted while load operation of the engine 10 is performed according tothe driver's pressing on the accelerator pedal 84, on the condition thatexecution of this routine is permitted by the HVECU 70, until thecatalyst temperature rise flag is turned off in step S170 of FIG. 3 .

At the start of the routine of FIG. 4 , the engine ECU 100 acquiresinformation required for the control, such as the intake air amount GA,the speed Ne, and the coolant temperature Tw of the engine 10, thetemperature Tpf of the particulate filter 190, the crank position fromthe crank angle sensor 90, and the required power Pe* and the targetspeed Ne* from the HVECU 70 (step S200). After the process of step S200,the engine ECU 100 determines whether or not the value of an enrichmentflag Fr is zero (step S210). Before the routine of FIG. 4 is started,the value of the enrichment flag Fr is set to zero, and when it isdetermined in step S210 that the value of the enrichment flag Fr is zero(step S210: NO), the engine ECU 100 sets the value of the enrichmentflag Fr to one (step S220).

Then, the engine ECU 100 sets fuel injection control amounts such as anamount of fuel injected from each port injection valve 15 p or eachcylinder injection valve 15 d and a fuel injection end timing (stepS230). In step S230, the engine ECU 100 sets to zero the amount of fuelinjected into one predetermined cylinder 11 (e.g., the first cylinder#1) among the cylinders 11 of the engine 10. In step S230, the engineECU 100 increases the amounts of fuel injected into the other cylinders11 (e.g., the second cylinder #2, the third cylinder #3, and the fourthcylinder #4) than the one cylinder 11 each by, for example, 20% to 25%(in this embodiment, 20%) compared with the amount of fuel to beoriginally injected into the one cylinder 11 (first cylinder #1).

After setting the fuel injection control amounts in step S230, theengine ECU 100 identifies a cylinder 11 for which a fuel injection starttiming has come based on the crank position from the crank angle sensor90 (step S240). When it is determined, as a result of the identificationprocess of step S240, that the fuel injection start timing for the onecylinder 11 (first cylinder #1) has come (step S250: NO), the engine ECU100 does not inject fuel from the port injection valve 15 p or thecylinder injection valve 15 d corresponding to this one cylinder 11, anddetermines whether or not one cycle of fuel injection to rotate theengine 10 twice has been completed (step S270). While fuel supply to theone cylinder (first cylinder #1) is stopped (during fuel cutoff), theintake valve and the exhaust valve of this cylinder 11 are opened andclosed in the same manner as when fuel is supplied thereto. When it isdetermined, as a result of the identification process of step S240, thatthe fuel injection start timing for one of the other cylinders 11 (thesecond cylinder #2, the third cylinder #3, or the fourth cylinder #4)has come (step S250: YES), the engine ECU 100 injects fuel into thatcylinder 11 from the corresponding port injection valve 15 p or cylinderinjection valve 15 d (step S260), and determines whether or not onecycle of fuel injection has been completed (step S270).

When it is determined in step S270 that one cycle of fuel injection hasnot yet been completed (step S270: NO), the engine ECU 100 repeatedlyexecutes the processes of steps S240 to S260. While this routine isexecuted, the opening degree of the throttle valve 14 is set based onthe required power Pe* and the target speed Ne* (required torque).Therefore, as a result of the processes of steps S240 to S270, fuelsupply to the one cylinder 11 (first cylinder #1) is stopped and theair-fuel ratios for the other cylinders 11 (the second cylinder #2, thethird cylinder #3, and the fourth cylinder #4) are enriched.Hereinafter, a cylinder 11 to which fuel supply is stopped will bereferred to as a “fuel-cutoff cylinder” where appropriate, and acylinder 11 to which fuel is supplied will be referred to as a“combustion cylinder” where appropriate. When it is determined in stepS270 that one cycle of fuel injection has been completed (step S270:YES), the engine ECU 100 re-executes the processes of step S200 and thesubsequent steps.

After setting the value of the enrichment flag Fr to one in step S220,the engine ECU 100 determines in step S210 that the value of theenrichment flag Fr is one (step S210: YES). In this case, the engine ECU100 determines whether or not the temperature Tpf of the particulatefilter 190 acquired in step S200 is lower than a predeterminedregeneration allowing temperature (first determination threshold value)Ty (step S215). The regeneration allowing temperature Ty is atemperature equal to or slightly higher than a lower limit value of thetemperature at which the particulate filter 190 can be regenerated,i.e., particulate matter can be combusted. The regeneration allowingtemperature Ty is determined in advance according to the serviceenvironment of the hybrid vehicle 1, and is, for example, a temperatureof around 650° C. in this embodiment. When it is determined in step S215that the temperature Tpf of the particulate filter 190 is lower than theregeneration allowing temperature Ty (step S215: YES), the engine ECU100 executes the processes of steps S230 to S270 and then re-executesthe processes of step S200 and the subsequent steps.

When it is determined in step S215 that the temperature Tpf of theparticulate filter 190 is equal to or higher than the regenerationallowing temperature Ty (step S215: NO), as shown in FIG. 5 , the engineECU 100 determines whether or not the value of a high temperature flagFt is zero (step S280). Before the routine of FIG. 4 is started, thevalue of the high temperature flag Ft is set to zero, and when it isdetermined in step S280 that the value of the high temperature flag Ftis zero (step S280: YES), the engine ECU 100 sets the value of theenrichment flag Fr to zero (step S290). After setting the value of theenrichment flag Fr to zero, the engine ECU 100 determines whether or notthe temperature Tpf of the particulate filter 190 acquired in step S200is equal to or higher than a predetermined regeneration promotingtemperature (second determination threshold value) Tz (step S300). Theregeneration promoting temperature Tz is a temperature at whichregeneration of the particulate filter 190, i.e., combustion ofparticulate matter can be promoted. The regeneration promotingtemperature Tz is determined in advance according to the serviceenvironment of the hybrid vehicle 1, and is, for example, a temperatureof around 700° C. in this embodiment.

When it is determined in step S300 that the temperature Tpf of theparticulate filter 190 is lower than the regeneration promotingtemperature Tz (step S300: NO), the engine ECU 100 sets the fuelinjection control amounts such as the amount of fuel injected from eachport injection valve 15 p or each cylinder injection valve 15 d and thefuel injection end timing (step S310). In step S310, the engine ECU 100sets the amount of fuel injected into the fuel-cutoff cylinder (firstcylinder #1) among the cylinders 11 to zero. In step S310, the engineECU 100 increases the amounts of fuel injected into all the othercylinders (the second cylinder #2, the third cylinder #3, and the fourthcylinder #4) than the fuel-cutoff cylinder (first cylinder #1) each by,for example, 3% to 7% (in this embodiment, 5%) compared with the amountof fuel to be originally injected into the fuel-cutoff cylinder.

After setting the fuel injection control amounts in step S310, theengine ECU 100 repeatedly executes the processes of steps S240 to S260until it is determined in step S270 that one cycle of fuel injection hasbeen completed. Thus, fuel supply to the one cylinder (fuel-cutoffcylinder) 11 (first cylinder #1) is stopped, and the air-fuel ratios forthe other cylinders (combustion cylinders) 11 (the second cylinder #2,the third cylinder #3, and the fourth cylinder #4) are changed towardthe lean side to slightly rich ratios compared with those when theprocess of step S230 is executed.

When it is determined in step S300 that the temperature Tpf of theparticulate filter 190 is equal to or higher than the regenerationpromoting temperature Tz (step S300: YES), the engine ECU 100 sets thevalue of the high temperature flag Ft to one (step S305). Further, instep S305, the engine ECU 100 sends a fuel-cutoff cylinder additionrequest signal for requesting addition of a fuel-cutoff cylinder to theHVECU 70. Then, the engine ECU 100 sets the fuel injection controlamounts for each port injection valve 15 p or each cylinder injectionvalve 15 d (step S310), and repeatedly executes the processes of stepsS240 to S260 until it is determined in step S270 that one cycle of fuelinjection has been completed.

In this embodiment, the engine ECU 100 sends the fuel-cutoff cylinderaddition request signal to the HVECU 70 once every two cycles (fourrotations of the engine 10) after setting the value of the hightemperature flag Ft to one in step S305. Whether or not to permitaddition of a fuel-cutoff cylinder is determined by the HVECU 70. Whenthe HVECU 70 permits addition of a fuel-cutoff cylinder, the engine ECU100 selects (adds), as a new fuel-cutoff cylinder, a cylinder 11 (inthis embodiment, the fourth cylinder #4) of which execution of fuelinjection (ignition) is not continuous with that of the first cylinder#1 when the catalyst temperature raising control routine is notexecuted.

Further, when the HVECU 70 permits addition of a fuel-cutoff cylinder,in step S310, the engine ECU 100 sets the amounts of fuel injected intothe fuel-cutoff cylinders (the first cylinder #1 and the fourth cylinder#4) among the cylinders 11 to zero. In step S310, the engine ECU 100increases the amounts of fuel injected into all the other combustioncylinders (the second cylinder #2 and the third cylinder #3) than thefuel-cutoff cylinders each by, for example, 3% to 7% (in thisembodiment, 5%) compared with the amount of fuel to be originallyinjected into one fuel-cutoff cylinder. Also in this case, after theprocess of step S310, the engine ECU 100 executes the processes of stepsS240 to S270 and then re-executes the processes of step S200 and thesubsequent steps. Thus, fuel supply to the two cylinders 11 (the firstcylinder #1 and the fourth cylinder #4) is stopped, and the air-fuelratios for the other cylinders 11 (the second cylinder #2 and the thirdcylinder #3) are changed toward the lean side to slightly rich ratioscompared with those when the process of step S230 is executed.

After setting the value of the high temperature flag Ft to one in stepS305, the engine ECU 100 determines in step S280 that the value of thehigh temperature flag Ft is one (step S280: NO). In this case, theengine ECU 100 determines whether or not the temperature Tpf of theparticulate filter 190 acquired in step S200 is lower than thetemperature raising control start temperature Tx (step S320). When it isdetermined in step S320 that the temperature Tpf of the particulatefilter 190 is equal to or higher than the temperature raising controlstart temperature Tx (step S320: NO), the engine ECU 100 executes theprocesses of steps S310 and S240 to S270 and then re-executes theprocesses of step S200 and the subsequent steps. On the other hand, whenit is determined in step S320 that the temperature Tpf of theparticulate filter 190 is lower than the temperature raising controlstart temperature Tx (step S320: YES), the engine ECU 100 sets the valueof the high temperature flag Ft to zero (step S325). Further, in stepS325, the engine ECU 100 sends a fuel-cutoff cylinder reduction signalto the HVECU 70 to notify the HVECU 70 of resumption of fuel supply tothat fuel-cutoff cylinder (fourth cylinder #4) that has been addedearlier.

After the process of step S325, the engine ECU 100 sets the value of theenrichment flag Fr to one again in step S220 of FIG. 4 . Further, theengine ECU 100 sets to zero the amount of fuel injected into thefuel-cutoff cylinder (first cylinder #1) of which stoppage of fuelsupply continues, and increases the amounts of fuel injected into theother cylinders (combustion cylinders) 11 (the second cylinder #2, thethird cylinder #3, and the fourth cylinder #4) each by 20% compared withthe amount of fuel to be originally injected into the one fuel-cutoffcylinder (first cylinder #1) (step S230). Thus, as a result of theprocesses of steps S240 to S270, fuel supply to the one cylinder(fuel-cutoff cylinder) 11 (first cylinder #1) is stopped and theair-fuel ratios for the other cylinders (combustion cylinders) 11 (thesecond cylinder #2, the third cylinder #3, and the fourth cylinder #4)are enriched again.

FIG. 6 is a flowchart illustrating a driving control routine that isexecuted by the HVECU 70 after the catalyst temperature rise requestsignal is sent by the engine ECU 100 in step S150 of FIG. 3 , repeatedlyat predetermined time intervals and concurrently with the catalysttemperature raising control routine.

At the start of the routine of FIG. 6 , the HVECU 70 acquiresinformation required for the control, such as the accelerator operationamount Acc; the vehicle speed V; the crank position from the crank anglesensor 90; the rotation speeds Nm1, Nm2 of the motor generators MG1,MG2; the SOC, the target charge-discharge electricity Pb*, the allowablecharge electricity Win, and the allowable discharge electricity Wout ofthe electricity storage device 40; whether or not the fuel-cutoffcylinder addition request signal and the fuel-cutoff cylinder reductionsignal have been received from the engine ECU 100; and the value of theenrichment flag Fr from the engine ECU 100 (step S400). Then, the HVECU70 sets the required torque Tr* based on the accelerator operationamount Acc and the vehicle speed V, and sets the required power Pe* ofthe engine 10 based on the required torque Tr* (required travel powerPd*), the target charge-discharge electricity Pb* of the electricitystorage device 40, etc. (step S410).

The HVECU 70 determines whether or not the catalyst temperature raisingcontrol routine of FIG. 4 and FIG. 5 is yet to be started by the engineECU 100 (step S420). When it is determined in step S420 that thecatalyst temperature raising control routine is yet to be started by theengine ECU 100 (step S420: YES), the HVECU 70 sets a predetermined valueNeref as the lower limit speed Nelim that is the lower limit value ofthe speed of the engine 10 (step S430). The value Neref is a valuelarger by, for example, about 400 rpm to 500 rpm than the lower limitvalue of the speed of the engine 10 when the catalyst temperatureraising control routine is not executed. The process of step S430 isskipped after the catalyst temperature raising control routine isstarted by the engine ECU 100.

After the process of step S420 or S430, the HVECU 70 derives, from a map(not shown), a speed which corresponds to the required power Pe* and atwhich the engine 10 can be efficiently operated, and sets the derivedspeed or the lower limit speed Nelim, whichever is higher, as the targetspeed Ne* of the engine 10 (step S440). In step S440, the HVECU 70 setsa value obtained by dividing the required power Pe* by the target speedNe* as the target torque Te* of the engine 10. Further, within theranges of the allowable charge electricity Win and the allowabledischarge electricity Wout of the electricity storage device 40, theHVECU 70 sets the torque command Tm1* for the motor generator MG1according to the target torque Te* and the target speed Ne*, and thetorque command Tm2* for the motor generator MG2 according to therequired torque Tr* and the torque command Tm1* (step S450).

Then, upon request from the engine ECU 100, the HVECU 70 determineswhether or not to permit execution of the catalyst temperature raisingcontrol routine, i.e., stoppage of fuel supply to some cylinders 11(hereinafter, “stoppage of fuel supply” will be referred to as “fuelcutoff” where appropriate) (step S460). In step S460, the HVECU 70calculates a driving torque shortage resulting from fuel cutoff of onecylinder 11, i.e., a torque that is not output from the engine 10 as aresult of fuel cutoff (hereinafter referred to as a “torque shortage”where appropriate). More specifically, the HVECU 70 calculates a torqueshortage by multiplying a value, obtained by dividing the requiredtorque Tr* set in step S410 by the number of cylinders n of the engine10 (in this embodiment, n=4), by a gear ratio G between the rotor of themotor generator MG2 and the drive shaft DS (=Tr*·G/n). Further, in stepS460, the HVECU 70 determines whether or not this torque shortage can becovered by the motor generator MG2 based on the torque shortage, thetorque commands Tm1*, Tm2* set in step S450, and the allowable chargeelectricity Win and the allowable discharge electricity Wout of theelectricity storage device 40. When the fuel-cutoff cylinder additionrequest signal or the fuel-cutoff cylinder reduction signal has beenreceived from the engine ECU 100, the HVECU 70 determines whether or notthe torque shortage can be covered, with an increase or a decrease inthe number of the fuel-cutoff cylinders taken into account.

When it is determined, as a result of the determination process of stepS460, that the driving torque shortage resulting from fuel cutoff ofsome (one or two) cylinders 11 can be covered by the motor generator MG2(step S470: YES), the HVECU 70 sends a fuel cutoff permit signal to theengine ECU 100 (step S480). The fuel cutoff permit signal includes asignal that permits fuel cutoff of only one cylinder 11 when thefuel-cutoff cylinder addition request signal is sent from the engine ECU100. When it is determined, as a result of the determination process ofstep S460, that the driving torque shortage resulting from fuel cutoffof some cylinders 11 cannot be covered by the motor generator MG2 (stepS470: NO), the HVECU 70 sends a fuel cutoff prohibit signal to theengine ECU 100 (step S485), and ends the routine of FIG. 6 for now. Inthis case, execution of the catalyst temperature raising control routineby the engine ECU 100 is canceled or stopped.

When the HVECU 70 sends the fuel cutoff permit signal to the engine ECU100 in step S480, the HVECU 70 sends the required power Pe* set in stepS410 and the target speed Ne* set in step S440 to the engine ECU 100(step S490). Further, the HVECU 70 identifies the cylinder 11 for whichthe fuel injection start timing will come next based on the crankposition from the crank angle sensor 90 (step S500). When it isdetermined, as a result of the identification process of step S500, thatthe fuel injection start timing for the fuel-cutoff cylinder (the firstcylinder #1, or both the first cylinder #1 and the fourth cylinder #4)will come (step S510: NO), the HVECU 70 re-sets the torque command Tm2*for the motor generator MG2 (step S515).

In step S515, the HVECU 70 sets the sum of the torque command Tm2* setin step S450 and the torque shortage (=Tr*·G/n) as a new torque commandTm2*. After the process of step S515, the HVECU 70 sends the torquecommand Tm1* set in step S450 and the torque command Tm2* re-set in stepS515 to the MGECU 55 (step S560), and ends the routine of FIG. 6 fornow. Thus, while fuel supply to one of the cylinders 11 of the engine 10is stopped (during fuel cutoff), the motor generator MG1 is controlledby the MGECU 55 so as to rotate the engine 10 at the target speed Ne*,and the motor generator MG2 is controlled by the MGECU 55 so as to coverthe torque shortage.

On the other hand, when it is determined, as a result of theidentification process of step S500, that the fuel injection starttiming for the combustion cylinders (the second cylinder #2 to thefourth cylinder #4, or both the second cylinder #2 and the thirdcylinder #3) will come (step S510: YES), the HVECU 70 determines whetheror not the value of the enrichment flag Fr acquired in step S400 is one(step S520). When it is determined in step S520 that the value of theenrichment flag Fr is one (step S520: YES), the HVECU 70 calculates,from the accelerator operation amount Acc or the target torque Te* andfrom a fuel increase rate (in this embodiment, 20%) for one combustioncylinder used in step S230 of FIG. 4 , an excess torque Tex (positivevalue) of the engine 10 resulting from enrichment of the air-fuel ratiofor one combustion cylinder (step S530).

Further, the HVECU 70 determines, based on the excess torque Tex, thetarget speed Ne* and the target torque Te* set in step S440, the torquecommand Tm1* set in step S450, the allowable charge electricity Win ofthe electricity storage device 40, etc., whether or not the electricitystorage device 40 can be charged with electricity that is generated bythe motor generator MG1 when the excess torque Tex is offset while theengine 10 is rotated at the target speed Ne* by the motor generator MG1(step S540). When it is determined in step S540 that the excess torqueTex can be offset by the motor generator MG1 (step S540: YES), the HVECU70 re-sets the torque commands Tm1*, Tm2* with the excess torque Textaken into account (step S550).

In step S550, the HVECU 70 sets a new torque command Tm1* by adding, tothe torque command Tm1* set in step S450, the value (negative value) ofa component of the excess torque Tex that acts on the motor generatorMG1 through the planetary gear 30. In step S550, the HVECU 70 sets a newtorque command Tm2* by decreasing, from the torque command Tm2*, thevalue (positive value) of a component of the excess torque Tex that istransmitted to the drive shaft DS through the planetary gear 30. Afterthe process of step S550, the HVECU 70 sends the re-set torque commandsTm1*, Tm2* to the MGECU 55 (step S560), and ends the routine of FIG. 6for now. Thus, when the excess torque Tex can be offset by the motorgenerator MG1, the motor generator MG1 is controlled by the MGECU 55 soas to rotate the engine 10 at the target speed Ne* and convert theexcess power of the engine 10 based on the excess torque Tex intoelectricity, while fuel is supplied to all the combustion cylindersother than the fuel-cutoff cylinder such that the air-fuel ratios forthese combustion cylinders are enriched in steps S230 to S270 of FIG. 4. Meanwhile, the motor generator MG2 is controlled by the MGECU 55 so asto output a torque according to the torque command Tm2* set in stepS450, without covering the torque shortage.

On the other hand, when it is determined in step S540 that the excesstorque Tex cannot be offset by the motor generator MG1 (step S540: NO),the HVECU 70 sends an ignition retard request signal for requestingretarding of the ignition timing to the engine ECU 100 (step S555).Further, the HVECU 70 sends the torque commands Tm1*, Tm2* set in stepS450 to the MGECU 55 (step S560), and ends the routine of FIG. 6 fornow. Thus, when the excess torque Tex cannot be offset by the motorgenerator MG1, the motor generator MG1 is controlled by the MGECU 55 soas to rotate the engine 10 at the target speed Ne*, while fuel issupplied to all the combustion cylinders other than the fuel-cutoffcylinder such that the air-fuel ratios for these combustion cylindersare enriched in steps S230 to S270 of FIG. 4 . Meanwhile, the motorgenerator MG2 is controlled by the MGECU 55 so as to output a torqueaccording to the torque command Tm2* set in step S450, without coveringthe torque shortage. Upon receiving the ignition retard request signalfrom the HVECU 70, as shown in FIG. 7 , the engine ECU 100 retards theignition timing for each combustion cylinder from an optimal ignitiontiming (MBT) such that the output torque of the engine 10 becomesequivalent to that when the air-fuel ratios for the combustion cylindersare set to the stoichiometric air-fuel ratio.

When it is determined in step S520 that the value of the enrichment flagFr is zero (step S520: NO), the HVECU 70 sends the torque commands Tm1*,Tm2* set in step S450 to the MGECU 55 (step S560), and ends the routineof FIG. 6 for now. Thus, when the value of the enrichment flag Fr iszero, the motor generator MG1 is controlled by the MGECU 55 so as torotate the engine 10 at the target speed Ne*, while fuel is supplied toall the combustion cylinders other than the fuel-cutoff cylinder suchthat the air-fuel ratios for these combustion cylinders assume a valueon the lean side (slightly rich value) in step S310 of FIG. 5 and stepsS240 to S270 of FIG. 4 . Meanwhile, the motor generator MG2 iscontrolled by the MGECU 55 so as to output a torque according to thetorque command Tm2* set in step S450, without covering the torqueshortage.

In the hybrid vehicle 1, as a result of execution of the routines shownin FIG. 3 to FIG. 6 , when the build-up amount Dpm of particulate matteron the particulate filter 190 of the downstream control apparatus 19becomes equal to or larger than the threshold value D1, the catalysttemperature rise request signal is sent from the engine ECU 100 to theHVECU 70 to raise the temperatures of the exhaust gas control catalyst180 of the upstream control apparatus 18 and the particulate filter 190of the downstream control apparatus 19 (step S150 of FIG. 3 ). When atemperature rise of the particulate filter 190 etc. is permitted by theHVECU 70, the engine ECU 100 executes the catalyst temperature raisingcontrol routine (FIG. 4 and FIG. 5 ) that involves stopping fuel supplyto at least one of the cylinders 11 of the engine 10 and supplying fuelto the other cylinders 11 while load operation of the engine 10 isperformed according to the driver's pressing on the accelerator pedal84. During execution of the catalyst temperature raising controlroutine, the HVECU 70 controls the motor generator MG2 as a motive powergenerating device so as to cover a torque shortage (driving powershortage) resulting from stoppage of fuel supply to at least one of thecylinders 11 (FIG. 6 ).

Thus, the torque shortage resulting from stoppage of fuel supply to someof the cylinders 11 can be covered by the motor generator MG2 with highaccuracy and responsiveness, and a torque according to the requiredtorque Tr* can be output to the wheels W during execution of thecatalyst temperature raising control routine. The HVECU 70 (and theMGECU 55) controls the motor generator MG2 (electric motor) so as tocover the torque shortage while fuel supply to at least one of thecylinders 11 is stopped (during fuel cutoff) (steps S515 and S560 ofFIG. 6 ). Thus, deterioration in the drivability of the hybrid vehicle 1can be highly reliably avoided during execution of the catalysttemperature raising control routine.

The HVECU 70 sets the lower limit speed Nelim of the engine 10 to behigher when the catalyst temperature raising control routine is beingexecuted than when the catalyst temperature raising control routine isnot being executed (step S430 of FIG. 6 ). This can shorten the timeduring which fuel supply to some cylinders 11 is stopped, i.e., the timeduring which no torque is output from the engine 10 due to fuel cutoff.Thus, the hybrid vehicle 1 can highly reliably prevent problems due tofuel cutoff of some cylinders 11 such as vibration of the engine 10 fromsurfacing.

When execution of the catalyst temperature raising control routine ispermitted by the HVECU 70 (time t1 in FIG. 8 ), the engine ECU 100 stopsfuel supply to one of the cylinders 11 (first cylinder #1) of the engine10 and enriches the air-fuel ratios for the other cylinders 11 (thesecond cylinder #2, the third cylinder #3, and the fourth cylinder #4)(steps S230 to S270 of FIG. 4 ). Thus, a relatively large amount of air,i.e., oxygen is introduced into the upstream and downstream controlapparatuses 18, 19 from the cylinder 11 (fuel-cutoff cylinder) to whichfuel supply is stopped, and a relatively large amount of uncombustedfuel is introduced into these apparatuses from the cylinders 11(combustion cylinders) to which fuel is supplied. Specifically, theupstream and downstream control apparatuses 18, 19 are supplied with anamount of air (that is not a lean atmospheric gas but air containingalmost no fuel components) roughly equal to the capacity (volume) of thecylinder 11 from the fuel-cutoff cylinder. As a result, during loadoperation of the engine 10, a relatively large amount of uncombustedfuel can be caused to react in the presence of sufficient oxygen, andthe temperatures of the exhaust gas control catalyst 180 and theparticulate filter 190 supporting an exhaust gas control catalyst can besufficiently and quickly raised with the heat of the reaction as shownin FIG. 8 .

While fuel is thus supplied to all the combustion cylinders other thanthe fuel-cutoff cylinder so as to enrich the air-fuel ratios for thesecombustion cylinders, the HVECU 70 (and the MGECU 55) controls the motorgenerator MG1 (second electric motor) so as to convert excess power ofthe engine 10 resulting from enrichment of the air-fuel ratios for theother cylinders 11 (combustion cylinders) into electricity (steps S510to S560 of FIG. 6 ). Thus, it is possible to avoid reducing the fuelefficiency of the engine 10 as a result of execution of the catalysttemperature raising control routine, without complicating the control ofthe motor generator MG2 that covers a torque shortage.

When charging of the electricity storage device 40 is limited and theexcess power of the engine 10 cannot be converted into electricity bythe motor generator MG1, the HVECU 70 sends the ignition retard requestsignal for requesting retarding of the ignition timing to the engine ECU100 (step S555 of FIG. 6 ). Upon receiving the ignition retard requestsignal, the engine ECU 100 retards the ignition timing for thecombustion cylinder from the optimal ignition timing (MBT). Thus, evenwhen charging of the electricity storage device 40 with electricitygenerated by the motor generator MG1 is limited, the drivability of thehybrid vehicle 1 can be reliably secured by avoiding an increase in theoutput torque of the engine 10 resulting from enrichment of the air-fuelratio for the combustion cylinder.

During execution of the catalyst temperature raising control, after thetemperature Tpf of the particulate filter 190 becomes equal to or higherthan the regeneration allowing temperature Ty (first determinationthreshold value) (time t2 in FIG. 8 ), the engine ECU 100 changes theair-fuel ratios for all the other cylinders 11 (combustion cylinders)toward the lean side to slightly rich ratios while stopping fuel supplyto the one cylinder 11 (first cylinder #1) (step S310 of FIG. 5 etc.).Further, during execution of the catalyst temperature raising control,after the temperature Tpf of the particulate filter 190 becomes equal toor higher than the regeneration promoting temperature Tz (seconddetermination threshold value) higher than the regeneration allowingtemperature Ty (time t3 in FIG. 8 ), the engine ECU 100 stops fuelsupply to one of the other cylinders 11 (fourth cylinder #4) (step S305of FIG. 5 etc.), on the condition that the torque shortage resultingfrom execution of the catalyst temperature raising control routine canbe covered by the motor generator MG2 (steps S460 to S480 of FIG. 6 ).

Thus, it is possible to supply more oxygen from more than onefuel-cutoff cylinder into the upstream and downstream controlapparatuses 18, 19 of which the temperatures have been sufficientlyraised, while stably operating the engine 10 in which fuel supply tosome cylinders 11 is stopped. Therefore, the hybrid vehicle 1 canintroduce a larger amount of oxygen from more than one fuel-cutoffcylinder into the particulate filter 190 of which the temperature hasbeen raised along with the temperature of the exhaust gas controlcatalyst, and thereby reliably combust particulate matter having builtup on the particulate filter 190. The hybrid vehicle 1 can also reliablymitigate S- and HC-poisoning of the exhaust gas control catalyst 180 ofthe upstream control apparatus 18.

When addition of a fuel-cutoff cylinder is permitted by the HVECU 70,the engine ECU 100 selects, as a new fuel-cutoff cylinder, the cylinder11 (fourth cylinder #4) of which execution of fuel injection (ignition)is not continuous with that of the one cylinder 11 (first cylinder #1)when the catalyst temperature raising control routine is not executed.Specifically, when stopping fuel supply to two cylinders (more than onecylinder) 11, the engine ECU 100 executes the catalyst temperatureraising control routine so as to supply fuel to at least one of thecylinders 11 after stopping fuel supply to one of the cylinders 11.Thus, stoppage of fuel supply to one cylinder 11 and that to anothercylinder 11 do not occur in succession, so that deterioration in termsof engine sound and fluctuation in torque output from the engine 10 canbe avoided.

When the temperature Tpf of the particulate filter 190 becomes lowerthan the temperature raising control start temperature Tx (time t4 inFIG. 8 ) after a fuel-cutoff cylinder is added, as shown in FIG. 8 , theengine ECU 100 reduces the number of the fuel-cutoff cylinders andenriches the air-fuel ratios for the cylinders 11 (combustion cylinders)to which fuel is supplied (step S325 of FIG. 5 and steps S220 to S270 ofFIG. 4 ). Thus, when the temperatures of the upstream and downstreamcontrol apparatuses 18, 19 decrease as a fuel-cutoff cylinder is addedand the amount of air introduced into these apparatuses increases, it ispossible to raise the temperatures of the upstream and downstreamcontrol apparatuses 18, 19 again by enriching the air-fuel ratios forthe combustion cylinders, and keep the temperatures of the upstream anddownstream control apparatuses 18, 19 from decreasing by reducing thenumber of fuel-cutoff cylinders so as to reduce the amount of airintroduced into these apparatuses.

When the build-up amount Dpm on the particulate filter 190 becomes equalto or smaller than the threshold value D0 (time t5 in FIG. 8 ), theengine ECU 100 turns the catalyst temperature rise flag off and ends thecatalyst temperature raising control routine. However, when the timeduring which the accelerator is pressed is relatively short and thebuild-up amount Dpm on the particulate filter 190 does not become equalto or smaller than the threshold value D0 during that time, the routinesof FIG. 4 to FIG. 6 are interrupted for now and resumed when the driverpresses on the accelerator pedal 84 next time.

As has been described above, during load operation of the engine 10, thehybrid vehicle 1 can sufficiently and quickly raise the temperatures ofthe upstream and downstream control apparatuses 18, 19 and supply asufficient amount of oxygen to the upstream and downstream controlapparatuses 18, 19 to regenerate the exhaust gas control catalyst 180and the particulate filter 190, while avoiding deteriorating thedrivability. The above-described catalyst temperature raising controlroutine can regenerate the particulate filter 190 by reliably combustingparticulate matter having built up on the particulate filter 190, evenin a low-temperature environment where a large amount of particulatematter tends to build up on the particulate filter 190, particularly inan extremely low-temperature environment where the daily meantemperature can fall below −20° C.

In the above embodiment, the air-fuel ratios for all the combustioncylinders other than the fuel-cutoff cylinder are enriched whenexecution of the catalyst temperature raising control routine ispermitted. However, the disclosure is not limited to this aspect. At thestart of the catalyst temperature raising control routine, the hybridvehicle 1 may set the air-fuel ratios for the combustion cylinders tothe stoichiometric air-fuel ratio instead of enriching the air-fuelratios for the combustion cylinders. The hybrid vehicle 1 having thisaspect takes more time to raise the temperatures of the upstream anddownstream control apparatuses 18, 19 than when the air-fuel ratios forthe combustion cylinders are enriched, but can cause uncombusted fuel toreact in the presence of sufficient oxygen and sufficiently raise thetemperatures of the upstream and downstream control apparatuses 18, 19with the heat of reaction. Moreover, with stoppage of fuel supply tosome cylinders 11 continued, a sufficient amount of oxygen can besupplied into the upstream and downstream control apparatuses 18, 19 ofwhich the temperatures have been raised.

In the above embodiment, the air-fuel ratios for all the combustioncylinders are changed toward the lean side after the temperature Tpf ofthe particulate filter 190 becomes equal to or higher than theregeneration allowing temperature Ty (first determination thresholdvalue). However, the disclosure is not limited to this aspect. Thehybrid vehicle 1 may maintain the air-fuel ratios for the othercylinders 11 than the fuel-cutoff cylinder at rich ratios until thetemperature Tpf of the particulate filter 190 reaches the regenerationpromoting temperature Tz (determination threshold value). After thetemperature Tpf becomes equal to or higher than the regenerationpromoting temperature Tz, the hybrid vehicle 1 may stop fuel supply toone of the other cylinders 11 and change the air-fuel ratio for acylinder 11 among the other cylinders 11 to which fuel supply is notstopped toward the lean side (to a slightly rich ratio), on thecondition that the torque shortage can be covered by the motor generatorMG2. The hybrid vehicle 1 having this aspect can supply more oxygen intothe upstream and downstream control apparatuses 18, 19 aftersufficiently and quickly raising the temperatures of the exhaust gascontrol catalyst 180 and the particulate filter 190.

In step S310 of FIG. 5 , the fuel injection amounts may be set such thatthe air-fuel ratios for all the combustion cylinders other than thefuel-cutoff cylinder become lean. When the temperature Tpf of theparticulate filter 190 becomes equal to or higher than the regenerationpromoting temperature Tz, the hybrid vehicle 1 may change the air-fuelratios for all the combustion cylinders other than the fuel-cutoffcylinder to lean ratios, as indicated by the long dashed double-shortdashed line in FIG. 8 , instead of adding a fuel-cutoff cylinder. Whenchanging the air-fuel ratios for the combustion cylinders duringexecution of the catalyst temperature raising control routine, thehybrid vehicle 1 may gradually change the air-fuel ratio for eachcombustion cylinder, for example, according to changes in thetemperature Tpf of the particulate filter 190, as indicated by thedashed line in FIG. 8 .

The hybrid vehicle 1 may convert the excess power of the engine 10resulting from enrichment of the air-fuel ratio for the combustioncylinder into electricity by the motor generator MG2 instead of themotor generator MG1. In this case, it is determined in step S540 of FIG.6 whether or not the electricity storage device 40 can be charged withelectricity that is generated by the motor generator MG2 when the excesstorque Tex is offset by the motor generator MG2. Then, in step S550 ofFIG. 6 , the torque command Tm2* is re-set by decreasing a torquecorresponding to the excess torque Tex from the torque command Tm2* setin step S450. In step S560, the torque command Tm1* set in step S450 andthe torque command Tm2* re-set in step S550 are sent to the MGECU 55.The ignition retard request signal may be sent to the engine ECU 100every time it is determined in step S520 of FIG. 6 that the value of theenrichment flag Fr is one. The hybrid vehicle 1 having these aspects canalso reliably secure the drivability by outputting a torque according tothe required torque Tr* to the wheels W when enriching the air-fuelratio for the combustion cylinder during execution of the catalysttemperature raising control routine.

The engine 10 of the hybrid vehicle 1 is an in-line engine, and thecatalyst temperature raising control routine is configured to stop fuelsupply to at least one cylinder 11 during one cycle. However, thedisclosure is not limited to this aspect. The engine 10 of the hybridvehicle 1 may be a V-engine, a horizontally opposed engine, or aW-engine in which each bank is provided with an exhaust gas controlapparatus. In this case, the catalyst temperature raising controlroutine can be configured such that fuel supply to at least one cylinderin each bank is stopped during one cycle. Thus, sufficient oxygen can besent to the exhaust gas control apparatus in each bank of the V-engineetc.

The downstream control apparatus 19 may include an exhaust gas controlcatalyst (three-way catalyst) disposed on the upstream side and aparticulate filter disposed downstream of this exhaust gas controlcatalyst. In this case, the upstream control apparatus 18 may be omittedfrom the hybrid vehicle 1. Alternatively, the downstream controlapparatus 19 may include only a particulate filter. In this case, whenthe temperature of the exhaust gas control catalyst of the upstreamcontrol apparatus 18 is raised by executing the catalyst temperatureraising control routine, the temperature of the downstream controlapparatus 19 (particulate filter 190) can be raised withhigh-temperature exhaust gas flowing in from the upstream controlapparatus 18.

In the hybrid vehicle 1, the motor generator MG1 may be coupled to thesun gear 31 of the planetary gear 30; the output member may be coupledto the ring gear 32; and the engine 10 and the motor generator MG2 maybe coupled to the planetary carrier 34. A stepped transmission may becoupled to the ring gear 32 of the planetary gear 30. The planetary gear30 of the hybrid vehicle 1 may be substituted by a four-element compoundplanetary gear mechanism including two planetary gears. In this case,the engine 10 may be coupled to an input element of the compoundplanetary gear mechanism; the output member may be coupled to an outputelement; the motor generator MG1 may be coupled to one of the other tworotating elements; and the motor generator MG2 may be coupled to theother rotating element. The compound planetary gear mechanism may beprovided with a clutch that couples together two of the four rotatingelements, and a brake that can fix one of the rotating elements so asnot to rotate. The hybrid vehicle 1 may be configured as a plug-inhybrid vehicle of which the electricity storage device 40 can be chargedwith electricity from an external power source, such as a householdpower source or a quick charger installed in a filling station. Thecontroller in this disclosure includes the ECUs (the HVECU 70, theengine ECU 100, the MGECU 55) in the hybrid vehicle 1.

FIG. 9 is a schematic configuration diagram showing another hybridvehicle 1B of this disclosure. Those components of the hybrid vehicle 1Bthat are the same as in the hybrid vehicle 1 will be denoted by the samereference signs and an overlapping description will be omitted.

The hybrid vehicle 1B shown in FIG. 9 is a series-parallel hybridvehicle including an engine (internal combustion engine) 10B having aplurality of cylinders (not shown), the motor generators (synchronousmotor-generators) MG1, MG2, and a transaxle 20B. The engine 10B includesthe upstream control apparatus 18 and the downstream control apparatus19 as exhaust gas control apparatuses. A crankshaft (not shown) of theengine 10B, the rotor of the motor generator MG1, and a wheel W1 arecoupled to the transaxle 20B. Further, the motor generator MG2 iscoupled to a wheel W2 different from the wheel W1. Alternatively, themotor generator MG2 may be coupled to the wheel W1. The transaxle 20Bmay include a stepped transmission, a continuously variabletransmission, a dual-clutch transmission, or the like.

When operation of the engine 10B is stopped, the hybrid vehicle 1B cantravel on a driving torque (driving power) from at least one of themotor generators MG1, MG2 that are driven with electricity from theelectricity storage device 40. The hybrid vehicle 1B can also convertall power from the engine 10B in load operation into electricity by themotor generator MG1, and drive the motor generator MG2 with electricityfrom the motor generator MG1. In addition, the hybrid vehicle 1B cantransmit a driving torque (driving power) from the engine 10B in loadoperation to the wheel W1 through the transaxle 20B.

In the hybrid vehicle 1B, the same catalyst temperature raising controlroutine as that shown in FIG. 4 and FIG. 5 is executed by an engine ECU(not shown) while a driving torque from the engine 10B in load operationis transmitted to the wheel W1 through the transaxle 20B. Duringexecution of the catalyst temperature raising control routine, the motorgenerator MG2 is controlled so as to cover a driving torque shortageresulting from fuel cutoff of some cylinders of the engine 10B. Thus,the hybrid vehicle 1B can achieve operational effects similar to thoseof the hybrid vehicle 1. In the hybrid vehicle 1B, the transmissionincluded in the transaxle 20B may be downshifted (the gear ratio may bechanged) as necessary so as to set the speed of the engine 10B to orabove a predetermined speed during execution of the catalyst temperatureraising control routine. Thus increasing the speed of the engine 10B canshorten the time during which fuel supply to some cylinders is stopped,so that problems such as vibration of the engine 10B can be highlyreliably prevented from surfacing.

FIG. 10 is a schematic configuration diagram showing yet another hybridvehicle 1C of this disclosure. Those components of the hybrid vehicle 1Cthat are the same as in the hybrid vehicle 1 etc. will be denoted by thesame reference signs and an overlapping description will be omitted.

The hybrid vehicle 1C shown in FIG. 10 is a series-parallel hybridvehicle including an engine (internal combustion engine) 10C having aplurality of cylinders (not shown), and the motor generators(synchronous motor-generators) MG1, MG2. In the hybrid vehicle 1C, acrankshaft of the engine 10C and the rotor of the motor generator MG1are coupled to a first shaft S1, and the motor generator MG1 can convertat least part of power from the engine 10C into electricity. The rotorof the motor generator MG2 is coupled to a second shaft S2 directly orthrough a power transmission mechanism 120 including a gear train, andthe second shaft S2 is coupled to the wheels W through the differentialgear 39 etc. Alternatively, the motor generator MG2 may be coupled toother wheels (not shown) than the wheels W. The hybrid vehicle 1Cfurther includes a clutch K that connects and disconnects the firstshaft S1 and the second shaft S2 to and from each other. In the hybridvehicle 1C, the power transmission mechanism 120, the clutch K, and thedifferential gear 39 may be included in the transaxle.

When the clutch K is engaged, the hybrid vehicle 1C can output a drivingtorque from the engine 10C to the second shaft S2, i.e., the wheels W.In the hybrid vehicle 1C, the same catalyst temperature raising controlroutine as that shown in FIG. 4 and FIG. 5 is executed by an engine ECU(not shown) while the crankshaft of the engine 10C and the second shaftS2, i.e., the wheels W are coupled together by the clutch K and loadoperation of the engine 10C is performed according to a drivers pressingon the accelerator pedal. During execution of the catalyst temperatureraising control routine, the motor generator MG2 is controlled so as tocover a driving torque shortage resulting from fuel cutoff of somecylinders of the engine 10C. Thus, the hybrid vehicle 1C can achieveoperational effects similar to those of the hybrid vehicle 1 etc.

FIG. 11 is a schematic configuration diagram showing another hybridvehicle 1D of this disclosure. Those components of the hybrid vehicle 1Dthat are the same as in the hybrid vehicle 1 etc. will be denoted by thesame reference signs and an overlapping description will be omitted.

The hybrid vehicle 1D shown in FIG. 11 is a parallel hybrid vehicleincluding: an engine (internal combustion engine) 10D having a pluralityof cylinders (not shown); a motor generator (synchronousmotor-generator) MG; a hydraulic clutch K0; a power transmission device21; an electricity storage device (high-voltage battery) 40D; anauxiliary battery (low-voltage battery) 42; a PCU 50D that drives themotor generator MG; an MGECU 55D that controls the PCU 50D; and a mainelectronic control unit (hereinafter referred to as a “main ECU”) 170that controls the engine 10D and the power transmission device 21. Theengine 10D includes the upstream control apparatus 18 and the downstreamcontrol apparatus 19 as exhaust gas control apparatuses, and acrankshaft of the engine 10D is coupled to an input member of the dampermechanism 24. The motor generator MG operates as an electric motor thatis driven with electricity from the electricity storage device 40D andgenerates a driving torque, and outputs a regenerative braking torque tobrake the hybrid vehicle 1D. The motor generator MG operates also as apower generator that converts at least part of power from the engine 10Din load operation into electricity. A rotor of the motor generator MG isfixed to an input shaft 21 i of the power transmission device 21 asshown in FIG. 11 .

The clutch K0 couples and uncouples an output member of the dampermechanism 24, i.e., the crankshaft of the engine 10D and the input shaft21 i, i.e., the rotor of the motor generator MG to and from each other.The power transmission device 21 includes a torque converter (fluidtransmission device) 22, a multi- or single-disc lock-up clutch 23, amechanical oil pump MOP, an electrically powered oil pump EOP, atransmission 25, and a hydraulic control device 27 that regulates thepressure of a working fluid. The transmission 25 is, for example, afour- to ten-speed automatic transmission, and includes a plurality ofplanetary gears, a plurality of clutches, and a plurality of brakes(frictional engaging elements). The transmission 25 changes the speed ofpower transmitted from the input shaft 21 i through either the torqueconverter 22 or the lock-up clutch 23 in multiple stages, and outputsthis power from an output shaft 21 o of the power transmission device 21to the drive shaft DS through the differential gear 39. Alternatively,the transmission 25 may be a mechanical continuously variabletransmission, a dual-clutch transmission, or the like. A clutch thatcouples and uncouples the rotor of the motor generator MG and the inputshaft 21 i of the power transmission device 21 to and from each othermay be disposed between the two (see the long dashed double-short dashedline in FIG. 11 ).

In the hybrid vehicle 1D, the same catalyst temperature raising controlroutine as that shown in FIG. 4 and FIG. 5 is executed by the main ECU170 while the crankshaft of the engine 10D and the input shaft 21 i,i.e., the motor generator MG are coupled together by the clutch K0 andload operation of the engine 10D is performed according to a driver'spressing on the accelerator pedal. During execution of the catalysttemperature raising control routine, the main ECU 170 and the MGECU 55Dcontrol the motor generator MG so as to cover a driving torque shortageresulting from fuel cutoff of some cylinders of the engine 10D. Thus,the hybrid vehicle 1D can achieve operational effects similar to thoseof the hybrid vehicle 1 etc. When the air-fuel ratio for the combustioncylinder is enriched in the hybrid vehicle 1D, excess power of theengine 10D may be converted into electricity by the motor generator MG,and an increase in the output torque of the engine 10D may be avoided byretarding the ignition timing. Further, in the hybrid vehicle 1D, thetransmission 25 may be downshifted (the gear ratio may be changed) asnecessary so as to set the speed of the engine 10D to or above apredetermined speed during execution of the catalyst temperature raisingcontrol routine. The controller in this disclosure includes the ECUs(the main ECU 170 and the MGECU 55D) in the hybrid vehicle 1D.

FIG. 12 is a schematic configuration diagram showing still anotherhybrid vehicle 1E of this disclosure. Those components of the hybridvehicle 1E that are the same as in the hybrid vehicle 1 etc. will bedenoted by the same reference signs and an overlapping description willbe omitted.

The hybrid vehicle 1E shown in FIG. 12 includes: an engine (internalcombustion engine) 10E having a plurality of cylinders (not shown); themotor generator (synchronous motor-generator) MG; a power transmissiondevice 21E; a high-voltage battery 40E; a low-voltage battery (auxiliarybattery) 42E; a DC-DC converter 44 connected to the high-voltage battery40E and the low-voltage battery 42E; an inverter 54 that drives themotor generator MG; an engine ECU 100E that controls the engine 10E; anMGECU 55E that controls the DC-DC converter 44 and the inverter 54; andan HVECU 70E that controls the entire vehicle. The engine 10E includesthe upstream control apparatus 18 and the downstream control apparatus19 as exhaust gas control apparatuses, and the crankshaft 12 of theengine 10E is coupled to an input member of a damper mechanism (notshown) included in the power transmission device 21E. The engine 10Efurther includes a starter 130 that outputs a cranking torque to thecrankshaft 12 and starts the engine 10E.

The rotor of the motor generator MG is coupled to an end of thecrankshaft 12 of the engine 10E on the opposite side from the powertransmission device 21E through a transmission mechanism 140. In thisembodiment, the transmission mechanism 140 is a wrapping transmissionmechanism, a gear mechanism, or a chain mechanism. Alternatively, themotor generator MG may be disposed between the engine 10E and the powertransmission device 21E, and may be a direct-current electric motor. Thepower transmission device 21E includes, in addition to the dampermechanism, a torque converter (fluid transmission device), a multi- orsingle-disc lock-up clutch, a transmission, and a hydraulic controldevice that regulates the pressure of a working fluid. The transmissionof the power transmission device 21E is a stepped transmission, amechanical continuously variable transmission, a dual-clutchtransmission, or the like.

The hybrid vehicle 1E can start the engine 10E by outputting a crankingtorque from the motor generator MG to the crankshaft 12 through thetransmission mechanism 140. While the hybrid vehicle 1E is traveling,the motor generator MG operates mainly as a power generator thatconverts part of power from the engine 10E in load operation intoelectricity, and is driven with electricity from the high-voltagebattery 40E as necessary to output a driving torque (assist torque) tothe crankshaft 12 of the engine 10E. Further, the motor generator MGoutputs a regenerative braking torque to the crankshaft 12 of the engine10E to brake the hybrid vehicle 1E.

Also in the hybrid vehicle 1E, the same catalyst temperature raisingcontrol routine as that shown in FIG. 4 and FIG. 5 is executed by theengine ECU 100E while load operation of the engine 10E is performedaccording to a driver's pressing on the accelerator pedal. Duringexecution of the catalyst temperature raising control routine, the HVECU70E and the MGECU 55E control the motor generator MG so as to cover adriving torque shortage resulting from fuel cutoff of some cylinders ofthe engine 10E. Thus, the hybrid vehicle 1E can achieve operationaleffects similar to those of the hybrid vehicle 1 etc. When the air-fuelratio for the combustion cylinder is enriched in the hybrid vehicle 1E,excess power of the engine 10E may be converted into electricity by themotor generator MG, and an increase in the output torque of the engine10E may be avoided by retarding the ignition timing. Further, in thehybrid vehicle 1E, the transmission of the power transmission device 21Emay be downshifted (the gear ratio may be changed) as necessary so as toset the speed of the engine 10E to or above a predetermined speed duringexecution of the catalyst temperature raising control routine. Thecontroller in this disclosure includes the ECUs (the HVECU 70E, theengine ECU 100E, and the MGECU 55E) in the hybrid vehicle 1E.

As has been described above, the hybrid vehicle of this disclosureincludes a multi-cylinder engine, an exhaust gas control apparatusincluding a catalyst that removes harmful components of exhaust gas fromthe multi-cylinder engine, an electric motor, and an electricity storagedevice that exchanges electricity with the electric motor. At least oneof the multi-cylinder engine and the electric motor outputs drivingpower to a wheel. The hybrid vehicle includes a controller that, uponrequest for raising the temperature of the catalyst during loadoperation of the multi-cylinder engine, executes catalyst temperatureraising control that involves stopping fuel supply to at least one ofcylinders and enriching air-fuel ratios for the other cylinders than theat least one cylinder, and controls the electric motor so as to cover adriving power shortage resulting from execution of the catalysttemperature raising control.

The controller of the hybrid vehicle of this disclosure is configuredto, upon request for raising the temperature of the catalyst during loadoperation of the multi-cylinder engine, execute the catalyst temperatureraising control that involves stopping fuel supply to at least one ofthe cylinders of the multi-cylinder engine and enriching the air-fuelratios for the other cylinders. Thus, during execution of the catalysttemperature raising control, a relatively large amount of air, i.e.,oxygen is introduced into the exhaust gas control apparatus from thecylinder to which fuel supply is stopped, and a relatively large amountof uncombusted fuel is introduced into the exhaust gas control apparatusfrom the cylinder to which fuel is supplied. As a result, it is possibleto cause a relatively large amount of uncombusted fuel to react in thepresence of sufficient oxygen and sufficiently and quickly raise thetemperature of the catalyst with the heat of the reaction during loadoperation of the multi-cylinder engine. With stoppage of fuel supply tosome cylinders continued, a sufficient amount of oxygen can be suppliedinto the exhaust gas control apparatus of which the temperature has beenraised. Moreover, during execution of the catalyst temperature raisingcontrol, the electric motor is controlled by the controller so as tocover a driving power shortage resulting from execution of the catalysttemperature raising control, i.e., stoppage of fuel supply to the atleast one cylinder. Thus, during execution of the catalyst temperatureraising control, a driving power shortage resulting from stoppage offuel supply to some cylinders can be covered by the electric motor withhigh accuracy and responsiveness, and driving power as required can beoutput to the wheels. Therefore, during load operation of themulti-cylinder engine, the hybrid vehicle of this disclosure cansufficiently and quickly raise the temperature of the catalyst of theexhaust gas control apparatus and supply a sufficient amount of oxygento the exhaust gas control apparatus while avoiding deteriorating thedrivability.

The controller may control the electric motor so as to cover the drivingpower shortage while fuel supply to the at least one cylinder isstopped. Thus, deterioration in the drivability of the vehicle can behighly reliably avoided when the catalyst temperature raising control isexecuted.

The controller may retard an ignition timing for the other cylinders soas to avoid an increase in an output of the multi-cylinder engineresulting from enrichment of the air-fuel ratios for the othercylinders. Thus, even when the air-fuel ratios for the cylinders towhich fuel is supplied during execution of the catalyst temperatureraising control are enriched, driving power as required can be output tothe wheels and the drivability of the vehicle can be reliably secured.Alternatively, excess power of the multi-cylinder engine resulting fromenrichment of the air-fuel ratios may be converted into electricity bythe electric motor.

The hybrid vehicle may further include a second electric motor thatconverts at least part of power from the multi-cylinder engine intoelectricity and exchanges electricity with the electricity storagedevice. The controller may control the second electric motor so as toconvert excess power of the multi-cylinder engine resulting fromenrichment of the air-fuel ratios for the other cylinders intoelectricity. Thus, it is possible to avoid reducing the fuel efficiencyof the multi-cylinder engine as a result of execution of the catalysttemperature raising control, without complicating the control of theelectric motor that covers a driving power shortage.

The controller may retard an ignition timing for the other cylinderswhen the second electric motor is unable to convert the excess power ofthe multi-cylinder engine into electricity. Thus, even when charging ofthe electricity storage device with electricity generated by the secondelectric motor is limited, the drivability of the vehicle can bereliably secured by avoiding an increase in the output of themulti-cylinder engine resulting from enrichment of the air-fuel ratios.

The hybrid vehicle may further include a transaxle that is coupled to anoutput shaft of the multi-cylinder engine, the second electric motor,and the wheel. The electric motor may output the driving power to thewheel or another wheel different from the wheel.

The exhaust gas control apparatus may include a particulate filter. In avehicle including such an exhaust gas control apparatus, a large amountof oxygen can be introduced from a cylinder to which fuel supply isstopped into the particulate filter of which the temperature has beenraised along with the temperature of the catalyst, and particulatematter having built up on the particulate filter can be reliablycombusted. Thus, the catalyst temperature raising control of thisdisclosure is extremely effective for regenerating a particulate filterin a low-temperature environment where a large amount of particulatematter tends to build up on the particulate filter. The particulatefilter may be disposed downstream of the catalyst and support acatalyst. The exhaust gas control apparatus may include an upstreamcontrol apparatus that includes a catalyst, and a downstream controlapparatus that includes at least a particulate filter and is disposeddownstream of the upstream control apparatus.

In the control method of a hybrid vehicle of this disclosure, the hybridvehicle includes a multi-cylinder engine, an exhaust gas controlapparatus including a catalyst that removes harmful components ofexhaust gas from the multi-cylinder engine, an electric motor, and anelectricity storage device that exchanges electricity with the electricmotor. At least one of the multi-cylinder engine and the electric motoroutputs driving power to a wheel. The control method of the hybridvehicle includes: upon request for raising the temperature of thecatalyst during load operation of the multi-cylinder engine, executingcatalyst temperature raising control that involves stopping fuel supplyto at least one of cylinders and enriching air-fuel ratios for the othercylinders than the at least one cylinder; and controlling the electricmotor so as to cover a driving power shortage resulting from executionof the catalyst temperature raising control.

During load operation of the multi-cylinder engine, this method cansufficiently and quickly raise the temperature of the catalyst of theexhaust gas control apparatus and supply a sufficient amount of oxygento the exhaust gas control apparatus while avoiding deteriorating thedrivability.

It should be understood that the applicable embodiment of thisdisclosure is in no way limited by the above embodiment but can bechanged in various ways within the extensive scope of the disclosure.The above embodiment is merely one specific form of this disclosuredescribed in the section SUMMARY, and is not intended to limit theelements of this disclosure described in that section.

This disclosure can be applied to the hybrid vehicle manufacturingindustry and the like.

What is claimed is:
 1. A hybrid vehicle comprising: a multi-cylinderengine; an exhaust gas control apparatus including a catalyst configuredto remove harmful components of exhaust gas from the multi-cylinderengine; an electric motor; an electricity storage device configured toexchange electricity with the electric motor; and a controllerconfigured to execute catalyst temperature raising control upon arequest for raising a temperature of the catalyst during load operationof the multi-cylinder engine in the hybrid vehicle in which at least oneof the multi-cylinder engine or the electric motor is configured tooutput driving power to a wheel, and control the electric motor so as tocover a driving power shortage resulting from execution of the catalysttemperature raising control, wherein the catalyst temperature raisingcontrol involves stopping fuel supply to at least one cylinder ofcylinders of the multi-cylinder engine and enriching air-fuel ratios forother cylinders of the cylinders of the multi-cylinder engine, the othercylinders being different from the at least one cylinder, and thecontroller is configured to, in response to determining that the drivingpower shortage resulting from the execution of the catalyst temperatureraising control is not coverable by the electric motor, prohibit theexecution of the catalyst temperature raising control when the catalysttemperature raising control has not started.
 2. The hybrid vehicleaccording to claim 1, wherein the controller is configured to controlthe electric motor so as to cover the driving power shortage while fuelsupply to the at least one cylinder of the multi-cylinder engine isstopped.
 3. The hybrid vehicle according to claim 1, wherein thecontroller is configured to retard an ignition timing for the othercylinders so as to avoid an increase in an output of the multi-cylinderengine resulting from enrichment of the air-fuel ratios for the othercylinders.
 4. The hybrid vehicle according to claim 1, furthercomprising a second electric motor configured to convert at least partof power from the multi-cylinder engine into electricity and to exchangeelectricity with the electricity storage device, wherein the controlleris configured to control the second electric motor so as to convertexcess power of the multi-cylinder engine resulting from enrichment ofthe air-fuel ratios for the other cylinders into electricity.
 5. Thehybrid vehicle according to claim 4, wherein the controller isconfigured to retard an ignition timing for the other cylinders when thesecond electric motor is unable to convert the excess power of themulti-cylinder engine into electricity.
 6. The hybrid vehicle accordingto claim 4, further comprising a transaxle that is coupled to an outputshaft of the multi-cylinder engine, the second electric motor, and thewheel, wherein the electric motor is configured to output the drivingpower to the wheel or another wheel different from the wheel.
 7. Thehybrid vehicle according to claim 1, wherein the exhaust gas controlapparatus includes a particulate filter.
 8. A control method of a hybridvehicle, the hybrid vehicle including a multi-cylinder engine, anexhaust gas control apparatus including a catalyst configured to removeharmful components of exhaust gas from the multi-cylinder engine, anelectric motor, and an electricity storage device configured to exchangeelectricity with the electric motor, at least one of the multi-cylinderengine or the electric motor being configured to output driving power toa wheel, the control method of the hybrid vehicle comprising: upon arequest for raising a temperature of the catalyst during load operationof the multi-cylinder engine, executing catalyst temperature raisingcontrol that involves stopping fuel supply to at least one cylinder ofcylinders of the multi-cylinder engine and enriching air-fuel ratios forother cylinders of the cylinders of the multi-cylinder engine, the othercylinders being different from the at least one cylinder; controllingthe electric motor so as to cover a driving power shortage resultingfrom execution of the catalyst temperature raising control; and inresponse to determining that the driving power shortage resulting fromthe execution of the catalyst temperature raising control is notcoverable by the electric motor, prohibiting the execution of thecatalyst temperature raising control when the catalyst temperatureraising control has not started.
 9. The hybrid vehicle according toclaim 1, wherein the controller is configured to calculate a drivingtorque shortage resulting from the execution of the catalyst temperatureraising control, determine whether the driving torque shortage iscoverable by the electric motor, and in response to determining that thedriving torque shortage is not coverable by the electric motor, prohibitthe execution of the catalyst temperature raising control when thecatalyst temperature raising control has not started.
 10. The controlmethod according to claim 8, further comprising: calculating a drivingtorque shortage resulting from the execution of the catalyst temperatureraising control; determining whether the driving torque shortage iscoverable by the electric motor; and in response to determining that thedriving torque shortage is not coverable by the electric motor,prohibiting the execution of the catalyst temperature raising controlwhen the catalyst temperature raising control has not started.